Background The recruitment maneuver (RM) has been shown to improve oxygenation in some patients with acute respiratory distress syndrome. But there is a lack of standardization and lack of clinical studies to prove the improvement on clinical outcome. We conducted this study to evaluate the clinical efficacy and safety of the RM in patients with acute respiratory distress syndrome (ARDS) using Iow tidal volume ventilation.Methods We randomly assigned 110 patients with ARDS from 14 Chinese intensive care units (ICUs) at the tertiary teaching hospitals. Patients with PaO2 ≤200 mmHg at FiO2 1.0 and PEEP ≥10 cmH2O were included in the study.Patients were randomized into two groups: control group and RM group. The tidal volume was set to 6-8 mi per kilogram of predicted body weight (PBW) in both groups. RM was performed by continuous positive airway pressure (CPAP) of 40 cmH2O maintained for 40 seconds. RMs was conducted every eight hours for the first five days, or stopped within five days if the patient reached the weaning standard.Results One hundred and ten patients had completed the requirements for the primary study goals, 55 from the RM group and 55 control patients. Baseline characteristics remained similar in the two groups. In the RM group the PaO2/FiO2 was significantly increased compared to baseline at 120 minutes after RM on day one and day two (P=0.007and P=0.001). There were no significant differences between the RM and control group in hospital mortality (41.8% vs.56.4%, P=0.13), 28-day mortality (29.1% vs. 43.6%, P=0.11) and ventilator-free days at day 28 (10.8±10.1 vs. 7.4±10.0,P=0.08). ICU mortality (32.7% vs. 52.7%, P=0.03), the rate of survival with unassisted breathing for at least 48 consecutive hours at day 28 (58.2% vs. 36.2%, P=0.02), and nonpulmonary organ failure-free days at day 28 (17.4±11.1vs. 13.0±12.0, P=0.03) favored the RM group. There was no significant difference in mean blood pressure and heart rate before RM and at 30, 60, 120 minutes after RM. There was no incidence of barotraumas.Conclusions RM was safe and useful for improving oxygenation in patients with ARDS who were ventilated with a low tidal volume, with a beneficial impact on their clinical outcome.